1. Field of the Invention
The present invention relates to a position adjusting mechanism having two screws of different pitches connected to each other, and an image scanning apparatus having such a position adjusting mechanism for positioning a guide member for guiding an image recording carrier.
2. Description of the Related Art
There is known a system for recording radiation image information of a subject such as a human body with a stimulable phosphor, and reproducing the recorded radiation image information on a photosensitive medium such as a photographic film, or displaying the recorded radiation image information on a display unit such as a CRT or the like.
The stimulable phosphor is a phosphor which, when exposed to an applied radiation (X-rays, xcex1-rays, xcex3-rays, electron beams, ultraviolet radiation, or the like), stores a part of the energy of the radiation, and, when subsequently exposed to applied stimulating rays such as visible light, emits light in proportion to the stored energy of the radiation. Usually, a sheet provided with a layer of the stimulable phosphor is used as a stimulable phosphor sheet.
The above known system includes an image information reading apparatus which comprises a reading unit for reading the recorded radiation image information carried on the stimulable phosphor sheet, and an erasing unit for erasing residual radiation image information remaining on the stimulable phosphor sheet after the recorded radiation image information has been read from the stimulable phosphor sheet. The image information reading apparatus also includes a loading unit for accommodating a cassette which stores a stimulable phosphor sheet with the radiation image information of a subject being recorded thereon by an external exposure device.
When the cassette is opened, a sheet picking means removes the stimulable phosphor sheet from the cassette, and the stimulable phosphor sheet is fed to the reading unit by a sheet feed means.
The reading unit has an auxiliary scanning feed mechanism, a laser beam applying means for applying a laser beam, and a light guide means. The auxiliary scanning feed mechanism has first and second roller pairs rotatable in synchronism with each other, and a guide member for guiding the stimulable phosphor sheet as it is fed toward or away from the first and second roller pairs. Each of the first and second roller pairs comprises a drive roller and a nip roller movable toward and away from the drive roller.
The stimulable phosphor sheet fed to the reading unit is guided by the guide member and the first roller pair to a laser beam applying. position between the first roller pair and the second roller pair.
The laser beam emitted from the laser beam applying means is applied to an image recording surface of the stimulable phosphor sheet. Upon exposure to the laser beam, the stimulable phosphor sheet emits light representing the stored image information toward the light guide means. The light is then guided to a light guide of the light guide means.
The light is applied to a photoelectric transducer mounted on the light guide, and converted into an electric signal by the photoelectric transducer. The electric signal is supplied to a display unit, which converts the electric signal into a light signal that is outputted as image information.
The stimulable phosphor sheet from which the image has thus been read is delivered to the erasing unit where remaining image information is erased from the stimulable phosphor sheet. Thereafter, the stimulable phosphor sheet is inserted back into the cassette in the loading unit for reuse.
The guide member of the auxiliary scanning feed mechanism needs to be positioned with high accuracy. If the guide member were positioned with low accuracy, then the laser beam would not be applied at a desired angle to the stimulable phosphor sheet, with the result that the image would not be displayed clearly on the display unit.
The guide member is usually positioned when the image information reading apparatus is manufactured. Specifically, the worker uses a leveler to position the four corners of the guide member at a predetermined height and then fixes the guide member that has been positioned. According to such a positioning process, it is highly difficult for the worker to displace the guide member slightly, and it is time-consuming for the worker to position the guide member highly accurately. The time-consuming positioning process tends to lower the efficiency of the production of the image information reading apparatus.
One known position adjusting mechanism comprises a right-hand screw connected to the upper end of a left-hand screw. When the right-hand screw is turned, the left-hand screw is turned in unison therewith, thus positionally displacing a member connected to the left-hand screw. Such a known position adjusting mechanism may be used to position the above guide member.
However, the known position adjusting mechanism is disadvantageous in that it produces a large displacement in one positioning operation. Since it is difficult for the position adjusting mechanism to displace the guide member slightly, it takes a long period of time to position the guide member with high accuracy. Another problem is that the manufacturing cost of the image information reading apparatus is high because the left-hand screw that needs to be used is more expensive than the right-hand screw.
It is a primary object of the present invention to provide a position adjusting mechanism which is capable of displacing a member simply and easily by a slight distance and can be manufactured at a low cost, and an image scanning apparatus which incorporates such a position adjusting mechanism.
Another object of the present invention is to provide an image scanning apparatus which prevents a guide member that has been positioned from being displaced.
Still another object of the present invention is to provide an image scanning apparatus which allows a turning means to be inserted easily into a support member and which is capable of positioning a guide member simply and easily by turning a second screw with the turning means.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.